Circuit interrupter



g- 1969 WASABURO MURAI ET AL 3,464,038

CIRCUIT INTERRUPTER 2 Sheets-Sheet 1 Filed Feb. 12 1968 FIG! INVENTORSWASABURO MURAI YOSHIO KOBAYASHI ATTORNEYS Filed Feb. 12, 1968 2Sheets-Sheet 2 INVENTORS WASABURO MURAI YOSHIO KOBAYASHI wmw/dATTORNEYS.

United States Patent 3,464,038 CIRCUIT INTERRUPTER Wasaburo Murai,Osaka, and Yoshio Kobayashi, Nara,

Japan, assignors to Terasaki Denki Sangyo Kabushiki Kaisha, Osaka, JapanFiled Feb. 12, 1968, Ser. No. 704,777 Claims priority, applicationJapan, Feb. 16, 1967, 42/9,548, 42/12,390 Int. Cl. H01h 75/00, 77/00,83/00 US. Cl. 335-46 5 Claims ABSTRACT OF THE DISCLOSURE A circuitinterrupter comprises a pair of movable contact arms disposed inparallel relationship in their closed positions and a movable slottedcoupling plate forming one side Wall of an arc-extinguishing chamber.The contact arms have the respective contact bearing portions extendingthrough a slot on the coupling plate in the arc-extinguishing chamber.Upon the occurrence of a shortcircuiting current one of the movablecontact arms is moved to its open position by the action of anelectromagnetic repulsion generated between both arms. A little laterafter this movement the associated overcurrent responsive trip device isoperated to move the other contact arm to its open position. Thismovement is accompanied by the movement of the coupling plate to returnthe one contact arm to its closed position.

This invention relates to improvements in a circuit interrupter disposedin US. Patent No. 3,327,407, issued Oct. 5, 1966, and owned by the sameassignor as the present application.

According to the cited patent, the circuit interrupter includes a pairof movable contact arms disposed in substantially parallel relationshipin their closed positions and a switching mechanism coupled to one ofthe arms to drive it from its closed position to its open position andvice versa, the other contact arm being arranged to respond to a flow ofheavy current such as shortcircuit current to be separated from the onecontact arm by the action of an electromagnetic repulsion generatedbetween both arms without any time delay while the one contact armremains stationary by the action of the switching mechanism with theresult that the associated circuit is interrupted within a very shortperiod of time. A little later after this interruption a thermallyresponsive and/ or electromagnetic tripping mechanism involved are or isoperated to put the one contact arm in its open position. Then as theelectromagnetic repulsion decrease the other contact arm returns back toits original position by the action of the associated spring resultingin the readiness for the subsequent closing operation.

An object of the invention is to provide in a circuit interrupter of thetype described in the preceding paragraph, improved means for smoothlyand reliably returning the other contact arm to its original closedposition to be ready for the subsequent closing operation.

Another object of the invention is to increase a distance between a pairof separated contact in a circuit interrupter of the type discribed inthe preceding paragraph to shorten the interruption time of theinterrupter thereby to increase the current limiting effect andaccordingly its interruption capability.

Still another object of the invention is to prevent the one contact armin a circuit interrupter of the type described in the precedingparagraph from bouncing from its open position to its closed positionupon interrupting a flow of heavy current thereby to prevent re-arcingacross a pair of contacts.

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An additional object of the invention is to provide an improvedarc-extinguishing chamber simple in construction.

Briefly, the invention accomplishes the above cited objects by theprovision of a circuit interrupte comprising a pair of movable contactarms disposed in substantially parallel relationship in their closedpositions, each of the contact arms being provided at one end with acontact and pivotably mounted on the other end portion on a pivot pin,an operating mechanism for switching one of the movable contact armsfrom its closed position to its open positions and vice versa, the othercontact arm having only the contacting function and including springmeans spanned between the same and a support member therefor to exert onthe other contact arm a force tending to rotate the latter toward itsclosed position, and overcurrent responsive trip means operativelycoupled to the operating mechanism, a flow of extraordinarily excessivecurrent through the interrupter generating an electromagnetic repulsionbetween the pair of movable contact arms to drive the other contact armin its open position independently of the trip means, the other contactarm being held in its open position through the reversal of the force ofthe spring means over the dead point thereof, characterized in that acoupling plate including a slot thereon is movably disposed so as tohave the contact bearing portions of both the contact arms movablyprojecting beyond said slot, and that a little later after the othercontact arm has been moved to it open position the overcurrentresponsive trip means perform a trip operation to cause the constrainedstated of the operating mechanism to collapse thereby to rotate the onecontact arm to its open position while the one contact arm actuates thecoupling plate to return the other contact arm back to its closedposition.

Preferably, the coupling plate may be slidably disposed in oppositeguide slots formed on a pair of electrically insulating partitionsdisposed in the interrupter.

In order to increase a distance between a pair of separated contacts,the slot on the coupling plate may be advantageously as long aspossible.

The coupling plate may be conveniently disposed adjacent the contacts intheir closed positions thereby to prevent the one contact arm frombouncing from its open position to its closed position upon interruptinga flow of heavy current.

The invention will become more readily apparent from the followingdetailed description taken in conjunction with the accompanying drawingsin which:

FIGURE 1 shows partly in longitudinal section and partly in elevation acircuit interrupter constructed in accordance with the principles of theinvention;

FIGURE 2 is a fragmental pictorial view of a pair of movable contactarms and a coupling plate operatively connecting both arms to eachother, with a cover removed;

FIGURE 3 is a plan view of the coupling plate illustrated in FIGURE 2;

FIGURES 4 to 7 inclusive fragmental elevational views illustrating thepositional relationship between the pair of contact arms and thecoupling plate in the various positions of the contact arms.

While the invention will be shown and described in connection with acircuit interrupter of three pole type, it is to be understood that thesame is equally applicable to circuit interrupters of single pole typeand other multiple pole types. Also it is to be understood that thecomponents common to all the poles will be illustrated and described interms of the central pole alone.

Referring now to the drawings and FIGURE 1 in particular, there isillustrated a three pole circuit interrupter constructed in accordancewith the principles of the invention. The circuit interrupterillustrated comprises a housing member 1 and a detachable cover member2. The housing and cover members 1 and 2 respectively may beconveniently made of any suitable electrically insulating plastic by themolding technique and constitute a closed enclosure. Within theenclosure a pair of movable contact arms 3 and 4 are disposed so as tobe substantially horizontally positioned in parallel relationship in theclosed position of the interrupter. The contact arms 3 and 4 are made ofany suitable electrically conductive material and have a pair ofcontacts 3a and 4a attached at their free ends respectively.

The lower contact arm 4 has the other end portion pivotably mounted on arotatable shaft 7 by a U-shaped support member 8 for rotation about theaxis of the shaft 7 and the support member 8 is rigidly secured on thebottom wall surface of the housing member 1. Disposed on either commonside of the lower contact arm 4 and the U-shaped support member 8 is ahelical spring 9 having one end hooked to a pin 10 extending through thecontact arm 4 and the other end secured to a pin 11 disposed on theU-shaped support member 8. The spring 9 serves to provide to the lowercontact 4a on the lower contact arm 4 a contact pressure under which thecontact 4a engages the upper contact 3a with the pressure directed inthe clockwise direction as viewed in FIG- URE 1.

As will be apparent hereinafter, the lower contact arm 4 is adapted torespond to a flow of extraordinarily excessive current such a flow ofshortcircuit current through the interrupter to be rotated in thecounterclockwise direction as viewed in FIGURE 1. In order to preventthe lower contact arm '4 from rotating in the clockwise direction asviewed in FIGURE 1 from its closed position, a stopper 12 is disposed onthe support member 8 as shown in the same figure. The lower contact arm4 also has the other end folded and connected by way of a fiexibleconductor 13 to the conductor 13a connected to a source terminal 14.

The upper contact arm 3 is connected by way of connecting shafts 5 and 6to a contact holder 15 having pivotably mounted thereon a holders shaft16 of any suitable electrically insulating material. The holder shaft 16is pivotably supported to the housing member 1 through a pair ofopposite support members (not shown) disposed on the opposite wallsurfaces of the housing member 1. Thus the contact arm 3 is adapted tobe rotatable from its closed position to its open position and viceversa about the axis of the holder shaft 16, along with an operatingmechanism for the arm as will be subsequently described. The uppercontact arm 3 is also electrically connected to a connector 17 through aflexible conductor 18.

In order to manually move the upper movable contact arm 3 from itsclosed position as illustrated in FIGURE 1 to its open position and viceversa, there is provided an operating mechanism generally designated bythe reference numeral 20. The operating mechanism comprises an operatinghandle 21 movably projecting beyond the cover member 2, a switchinglever 22 secured at one end to the operating handle 21 and pivotablymounted at the other end on a stationary pin 19 secured to a fixtureblock 23, and a pair of toggle link members 24 and 25 articulated by atoggle pin 26. The mechanism further comprises a pair of tension springs27 spanned between a spring shoe 22a disposed at that end of theswitching lever 22 integrally connected to the operating handle 21 andspring shoe 26a loosely engaging the toggle pin 26. Thus it will beappreciated that the link members 24 and 25, the toggle pin 26 and thesprings 27 form a toggle linkage of the well known construction.

The operating mechanism is operatively coupled to a trip mechanism ofthe conventional design generally designated by the reference numeral28. More specifically,

the link member 25 engages at 29 to a trip lever 30 pivotably mounted atone end on a stationary pin 31 secured to the fixture block 23 andengaging at the other end a hook 32. Then the book 32 is adapted torespond to a flow of overload current through the interrupter to bereleased,

The interrupter also comprises a thermally responsive device generallydesignated by the reference numeral 35 for the purpose of tripping theinterrupter upon the occurrence of a flow of ordinary overload current.The thermally responsive device 35 includes a bimetal element 36electrically connected to the connector 17 through a conductor 37, and aU-shaped electric resistor 38 disposed adjacent the bimetallic element36. The resistor 38 has one end connected to the conductor 37 and theother end connected to another conductor 39 which is, in turn, connectedto a load terminal 40. As shown in FIGURE 1, an adjusting screw 41 issecured integrally at the free end of the bimetallic element 36. Uponthe occurrence of a flow of ordinary the resistor 38 and hence thebimetallic element 36 will be heated whereby the element is bentleftwardly as viewed in FIGURE 1 to push against a trip piece 42 facingthe same. This causes a trip shaft 43 integral with the trip piece 42 tobe rotated to disengage a catch 44 secured to the trip shaft 43 from thehook 32 resulting in a tripping operation.

If an excessive current whose magnitude may be in the order of 8 to 10times the rating current flows through the interrupter then anelectromagnet device including a stationary and a movable iron core 45and 46 respectively is energized to perform an instantaneously trippingoperation. More specifically, the stationary iron core 45 is excitedwith an excessive current such as above described flowing through theconductor 37 disposed adjacent the same to attract the movable iron core46 thereby to rotate the trip shaft 43 to disengage the catch 44 fromthe book 32 resulting in an instantaneously tripping operation.

As in the conventional type of three pole circuit interrupters, thehousing member 1 includes a pair of electrically insulating partitionwalls 1 and 1 to divide, along with both side walls, the interior intothree compartments in each of which the movable contact arms 3 and 4,the overcurrent responsive trip devices 35, 4546, 28, anarcextinguishing chamber 47 (see FIGURE 1), etc. for one pole aredisposed.

According to the principles of the invention, a slotted coupling plate50 of any suitable electrically insulating material is provided one foreach pole for the purpose of effecting resetting or returning movementof the lower moved contact arm 4 attendant with a tripping or openingmovement of the upper contact arm 3. The coupling plate 50 is providedwith a central longitudinal slot 52 as best shown in FIGURE 3 andslidably disposed in a pair of longitudinal guide grooves 54, 54' formedin opposite relationship on each pair of the opposed wall surfaces andin such positions that the contact bearing portions of both the contactarms 3 and 4 movably project beyond the slot 52 on the coupling plate 50as best shown in FIGURE 2. The plate 50 also serves to provide one sidewall of the chamber 47.

As shown in FIGURE 3, the slot 52 on the coupling plate 50 has anenlarged portion 52a through which the free end portions of the contactarms 3 and 4 can be inserted into the slot, and a pair of transverseedges 52b and c. The slot 52 has a width sufficient to permit thecontact bearing portions of the arms 3 and 4 to be freely movedthereinand serves to bring the lower contact arm 4 from its open position toits original closed position through movement of the upper contact arm 3from its closed position to its open position as will be describedhereinafter.

If an extraordinarily excessive current such as a shortcircuitingcurrent flows through the circuit interrupter in the closed positionwhere the upper and lower contact arms 3 and 4 respectively are in theirclosed positions as shown in FIGURE 4 then such a current will flowthrough both contact arms disposed in parallel, in the opposite paralleldirections which generates an electromagnetic repulsion between bothcontact arms. This electromagnetic repulsion does not affect the uppercontact arm 3 because the latter is constrained by the switching oroperating mechanism 20, but it overcomes a force provided by the spring9 to impart to the lower contact 4a a contact pressure whereupon thelower contact arm 4 is permitted to be rotated within the slot 52 on thecoupling plate 50 in the counterclockwise direction as viewed in FIGURE4 until the line of application of the spring 9 passing through the axesof the shafts and 11 is downwardly moved over the shaft 7. This causesthe force of the spring 9 to reverse in direction thereby to strike thecontact arm 4 against the lower edge 520 of the slot 52 as viewed inFIGURE 3, to depress the coupling plate 50. At the same time, thecontact arm 4 is rapidly rotated in the counterclockwise direction asviewed in FIGURES 1 and 5 until it strikes against a piece 48 of sheetvulcanized fiber disposed on the bottom of the housing member 1 (seeFIG- URE l) and is held in its open position as shown in FIG- URE 5 evenafter termination of the shortcircuiting current.

This separation of the lower contact arm 4 from the upper contact arm 3is effective for limiting or interrupting the shortcircuiting current.

A little later after this interruption the overcurrent responsive tripmechanism is operated to cause the constrained state of the operatingmechanism 20 to collapse to rotate the upper contact arm 3 in theclockwise direction as viewed in FIGURE 6 within the slot 52 on thecoupling plate 50. When the upper contact arm 3 has been rotated througha certain angle it will strike against the upper edge 52b as viewed inFIGURE 3 of the slot 52 (see FIGURE 6) thereby to raise the couplingplate 50. This is accompanied by lifting of the lower contact arm 4previously engaged by the lower edge 520 of the slot 52. Upon the lowercontact arm 4 reaching its position as shown at solid line in FIGURE 7where the line of application of the spring 9 passes through its deadpoint, it will return back to its original closed position as shown atdotted line in FIGURE 7 by its own inertia.

Under these circumstances, the stopper 12 prevents the arm 4 fromfurther rotating in the same direction. Then the interrupter can beresetted in the conventional manner to be ready for the succeedingclosing operation.

The invention has several advantages. For example, upon interrupting ashortcircuiting current through the utilization of an electromagneticrepulsion generated between the upper and lower contact arms 3 and 4 thelower contact arm 4 is held in its open position through the re-versealof the force of the associated spring 9 insurring that the openingoperation is performed to interrupt the associated circuit. A littlelater after this interruption the overcurrent responsive trip mechanismis operated to rotate the upper contact arm toward its open position.Attendant on this rotational movement of the upper contact arm 3, thelower contact arm 4 previously put in its open position and engaging thelower edge 52c of the slot 52 on the coupling plate 50 returns back toits original closed position to be ready for the succeeding closingoperation. This eliminates the necessity of locking the lower contactarm 4 to its open position by a latch or the like with the result thatthe lower contact arm is smoothly driven to and held in its openposition and returns back to its original closed position.

It has been found to be preferable that the length of the slot 52 on thecoupling plate 50 should be chosen to be so great that during itsopening movement the upper contact arm 3 strikes against the upper edge52b of the slot 52 to raise the lower contact arm 4 from its positionwhere it engages the lower edge 520 of the slot to its position wherethe force of the associated spring 9 reverses in direction, along withthe coupling plate 50.

Thereafter the upper contact arm 3 continues to effect the openingmovement to raise the coupling plate 50 and thence the lower contact arm4 until the lower arm is stopped by the stopper 12 whereupon it reachesits closed position and simultaneously the upper arm reaches and is heldin its open position.

This measure permits both contacts 3a and 4a to be separated from eachother to such an extent that the contact arms abut against the upper andlower edges of the slot respectively leading to a longer distance bywhich the contact 3a is separated from the contact 4a.

It is well known that although only the opening movement of the lowercontact arm 4 is generally effective for completing to interrupt a flowof shortcircuiting current through the interrupter that a flow ofshortcircuiting current approximately corresponding to the upper limitof the interruption capability of the interrupter itself may not becompletely interrupted through the completion of opening movement of thelower contact arm 4 as shown in FIGURE 5. Under these circumstances, theinvention is efiective for increasing a distance of separation betweenboth contacts through an opening movement of the upper contact arm 4effected a little later after the completion of opening movement of thelower contact arm as shown in FIGURE 6. This insures that any arecurrent is prevented from flowing between the separated contacts and theinterruption time additionally decreases resulting in increases in boththe current limiting effect and the interruption capability.

Also upon interrupting a flow of heavy current, one of movable contactarms such as the upper contact arm 3 is generally moved to its openposition where it strikes against the associated stopper. This generatesan impulse by which the contact arm may bounce in a direction to closeit causing re-arcing or re-closing. According to the invention, however,the coupling plate 50 is disposed in the vicinity of the contacts 3a and4a in their closed positions. Therefore an excessive kinetic energy ofthe upper contact arm 3 resulting from its opening movement iseffectively spent in raising the lower contact arm 4 from its openposition with the result that the upper contact arm is prevented frombouncing leading to rearcing and/or re-closing.

In addition the coupling plate 50 of any suitable electricallyinsulating material constitutes one side wall of the arc-extinguishingchamber 47. Therefore the resulting construction is not only simple butalso there are provided means for effectively preventing the operatingmechanism and the other components from thermally damaging due to a flowof arc current and diffusion of arced gases occurring upon interruptingan excessive current flowing through the interrupter and alsoshortcircuit across poles from occurring through the components.

While the invention has been illustrated and described in conjunctionwith a single preferred embodiment thereof it is to be understood thatvarious changes in the details of construction and the combination andarrangement of parts may be resorted to without departing from thespirit and scope of the invention.

What we claim is:

1. A circuit interrupter comprising a pair of movable contact armsdisposed in substantially parallel relationship in their closedpositions, each of the contact arms being provided at one end with acontact and pivotably mounted on the other end portion on a pivot pin,an operating mechanism for switching one of the movable contact armsfrom its closed position to its open position and vice versa, the othercontact arm having only the contacting function and including springmeans spanned between the same and a support member therefor to exert onthe other contact arm a force tending to rotate the latter toward itsclosed position, an overcurrent responsive trip means operativelycoupled to the operating mechanism, a flow of extraordinarily excessivecurrent through the interrupter generating an electromagnetic repulsionbetween the pair of movable contact arms to drive the other contact armin its open position independently of the trip means, the other contactarm being held in its open position through the reversal of the force ofthe spring means over the dead point therefor, wherein a coupling plateincluding a slot thereon is movably disposed so as to cause the contactbearing portions of both said contact arms to movably project beyondsaid slot, and that a little later after the other contact arm has beenmoved to its open position said overcurrent responsive trip meansperform a trip operation to cause the constrained state of saidoperating mechanism to collapse thereby to rotate the one contact arm toits open position while the one contact arm actuates said coupling plateto return the other contact arm back to its closed position.

2. A circuit interrupter as claimed in claim 1, wherein the interrupteris of multiple pole type and said coupling plate is slidably disposed ina pair of guide grooves formed in opposite relationship on a pair ofelectrically insulating walls for each pole.

3. A circuit interrupter as claimed in claim 1, wherein said slot onsaid coupling plate has a length sufiicient to raise the other contactarm from its closed position to its position where the force of saidspring means reverses in direction through opening movement of the onecontact arm thereby to increase a distance of separation between bothsaid contacts.

4. A circuit interrupter as claimed in claim 1, wherein said couplingplate is disposed in the vicinity of said contacts whereby an excessivekinetic energy of the one contact arm resulting from its openingmovement upon in terrupting a flow of excessive overcurrent through theinterrupter is spent in raising the other contact arm from its openposition thereby to prevent the one contact arm from bouncing to itsclosed position.

5. A circuit interrupter as claimed in claim 1, wherein said couplingplate of electrically insulating material form one side wall of anarc-extinguishing chamber in which an arc-extinguishing device isdisposed for each pole and said contact arms have their contact bearingportions mova'bly projecting through said slot on said coupling slotinto said arc-extinguishing chamber.

References Cited UNITED STATES PATENTS 3,127,488 3/1964 Bodenschatz335-16 FOREIGN PATENTS 1,238,994 4/ 1967 Germany.

BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner

